\section{Introduction}
 
As stated in the current NSAC Long-Range Plan \cite{Geesaman:2015fha}:
``[t]he new capabilities of the 12-GeV 
era facilitate a detailed study of baryons containing two 
and three strange quarks. Knowledge of the spectrum of 
these states will further enhance our understanding of 
the manifestation of QCD in the three-quark arena.''
Concerted efforts over the past several decades have helped identify
and characterize many excited states for the lightest baryon - the nucleon -
and for the lightest mesons. 
The vast amount of information gleaned  for the lightest hadrons
has led to tremendous progress in arriving at a description of
those particles using QCD. Yet, these very same detailed measurements 
have deepened the mystery of why such QCD-based descriptions of 
nucleon excited states invariably predict many more states than observed---
the so-called ``missing resonance'' problem.

Going beyond the lightest hadrons, progress towards a clearer understanding
of heavier hadrons containing one or more strange quarks arguably has been much slower.
Flavor symmetry predicts a spectrum of excited states
for heavier baryons at least as rich as that for the nucleon. 
Furthermore, the existence of hybrid mesons are a natural extension of the
constituent quark model when real excitations of gluonic fields are allowed.
Naively, with the presence of one or more strange quarks, 
one might think QCD-based descriptions for those heavier particles
would be more straightforward, robust, and successful 
than those currently attainable for the nucleon and the lightest mesons.
However, comparatively very little data exists for those heavier particles, and 
experimental evidence for predicted hybrid and other exotic meson states 
remains tenuous and controversial.
Major improvements in our empirical knowledge of the properties of these states   
should lead directly to 
advances in QCD descriptions of all hadrons,
including better predictions for 
the lightest particles consisting solely of up or down quarks.

This proposal seeks support for a program of measurements that will provide
major improvements in our knowledge of hadron spectroscopy, 
focused on activities at Jefferson Lab (JLab) (1) within Hall B  using
the CEBAF Large Acceptance Spectrometer (CLAS) newly upgraded for 
experiments using the 12 GeV beam at JLab (CLAS12)
and (2)  within Hall D using the GlueX detector.
ASU will conduct investigations with two large international collaborations  to
provide data which will be critical to advancing our
understanding of  how quarks and gluons assemble into 
mesons and baryons.
Both the Hall B and the Hall D activities outlined below 
seek to identify heretofore unobserved excited states of multi-quark systems and
to clarify the properties of those states
so that theoretical models of those multi-quark systems will be informed by
the most accurate and complete database possible.

We will obtain and analyze data using the newly-built CLAS12 detector
to explore the spectrum of multi-strange-quark (``very strange'') baryons. ASU 
simulations already have helped establish the initial running configuration for CLAS12, 
and confirmed the feasibility of our experimental program. 
Our extensive experience in meson photoproduction with CLAS during the 6 GeV era 
and our interests in hybrid and exotic
mesons led us to extend our program to the Hall D facilities,
which we have helped bring to full operation, because
those facilities were specifically tailored to carry out searches for those particles. 

Based on our prior experience with polarized photon beams in Hall B during the 6 GeV era,
the ASU Meson Physics Group successfully proposed, designed, built, and now operates 
a first-of-its-kind triplet-photoproduction photon-polarimeter (TPOL)
for the Hall D linearly-polarized photon beam. 
The TPOL device, discussed more fully in section 2.2.2,
precisely characterizes the degree of polarization of the photon beam in Hall D.
Thus, beyond the fundamental physics goals of our research program described above, 
our group will remain responsible for determining the polarization of the photon beam 
for all experiments in Hall D.
This contribution is critical: only precise knowledge of the Hall D photon beam can
empower the full exploitation of Hall D's capabilities
to probe the physics of hybrid and exotic hadrons with GlueX,
as well as to carry out the studies proposed here. 

The program outlined in the following sections, 
will obtain precise, extensive data
detailing the excitation spectra of two- and three-quark systems,
including previously unobserved or poorly-measured three-quark states,
as well as hybrid mesons.
No comprehensive QCD-based description of how hadrons are built from quarks
and gluons can be achieved without such information. 
Two complementary approaches will be pursued:

\begin{enumerate}

\item Working with the CLAS Collaboration,
ASU will lead an experiment with the newly-installed
CLAS12 detector in Hall B
to study excitations of $\Omega^-$ and $\Xi$ baryons
using quasi-real incident photons. These data will
produce the largest sample of
photoproduced $\Xi$ baryons ever, elucidating the excitation spectrum for that hadron,
and also yield the first data on
photoproduced $\Omega^-$ baryons.
The availability of a large sample of excited $\Xi$ states
will allow
measurement of poorly-known decay modes, many of which are
currently listed simply as
``seen'' or ``small'' within the current PDG summary \cite{Olive:2016xmw}.

\item
Working with the GlueX Collaboration,
the ASU group will participate in the search 
%using the GlueX detector 
for exotic hadrons with masses up to $2.5$~GeV, with
a particular emphasis on identifying the $\eta^{\prime}_1$ hybrid meson 
to rule out potential tetra-quark states.
Identifying such particles requires the determination of exotic
quantum numbers $J^{PC}$ that do not correspond to those seen in the
traditional constituent
quark model. 
Accurate knowledge of the energy and degree of polarization of the
tagged photon beam is mandatory for all
analyses in Hall D, and ASU's TPOL will provide
direct measurements of the photon beam polarization for all experiments in Hall D.
\end{enumerate}

Currently, the ASU Meson Physics Group is comprised of the principal investigator 
Associate Professor Michael Dugger, co-investigator Professor Barry Ritchie,
Graduate Research Associate Sebastian Cole, 
and sophomore undergraduate student Eric Bryan.
The proposal seeks steady-state funding for supporting the
principal investigator (PI), co-investigator, 
two graduate students, 
and an undergraduate student. 
